^You forget the exterior close-up of the bridge windows during the second or third attack (they're tiny on the outside)
This?
http://movies.trekcore.com/gallery/albums/xihd/trekxihd0138.jpg
Just goes to confirm the top part of the superstructure is the bridge, i.e., represents the height of one deck. And the saucer is the same thickness as the bridge height, as it should be for a 250 m ship.
the corridor network behind the bridge
No real problem there: the ship has a spine that extends back from the bridge, and can accommodate those corridors even if/when the bridge is represented by the circular part visible to the outside.
In addition, the lower part of that spine, as well as the secondary hull, appear to feature docking ports. If they are approximately two meters across, then the 250 m size is again supported. Although admittedly NX-01 had ports that are smaller than an upright man.
the HUGE chamber Robau's lift exits into
About the height of the dorsal hull in a 250 m ship.
We also see a Kelvin-style hull cut in half, exposing the decks, when Enterprise drops out of warp over Vulcan.
That ship is not the
Kelvin, though. Parts of the
Kelvin CGI model were stretched, truncated and mangled to create the cadet-crewed ships, establishing that there's not just one size for engines of that shape, and supposedly not just one size for saucers, either.
It would appear that even if the
Kelvin was conceptually enlarged during the writing or filming process, no effort was made to alter her design to reflect the new size. And since we never see the
Kelvin compared directly against the new
Enterprise or the cadet fleet ships, we don't really have a pressing reason to believe in the size increase.
Here's a quick sketch of what the two "variants" of
Saladin would look like side by side. Note the similarly sized bridges and similar saucer thicknesses, minus the infamous half-deck of the TOS saucer. The engine sizes match, too; the rest is added superstructure.
Timo Saloniemi